BF2 has many mods that can be played via lan. Our modding group produced a COOP online Multi-player version of BF2 for Special Forces that has everything you need for setting up and playing a Lan with COOP against bots.

WOW thanks everyone for your replies, i dont like enemy territory, so thats out of the picture, i already have halo and a *cough* crack *cough* to get around the individual keys, medal of honor i will get thanks!!!
i will also look into trackmainia nations.

Hey Guys and Gals
First time on the site,MOH is not a coop mission based game (unless you have 2 teams of 2 obviously) but is quite good,COD is an excellent LAN game with use of tanks,artillery,jeeps etc, a real gem,Vietcong is real good coop game against enemy but it requires some pretty heavy hardware to cope with the game,Blackhawk Down is excellent with use of the Blackhawks with mini-guns but is not coop,hope that helps